/*******************************************************************************
 * Copyright (c) 2004, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.equinox.internal.p2.core;

import java.io.*;
import java.nio.channels.FileLock;
import org.eclipse.osgi.util.NLS;

/**
 * Internal class.
 */
public class Locker_JavaNio implements Locker {
	private File lockFile;
	private FileLock fileLock;
	private RandomAccessFile raFile;

	public Locker_JavaNio(File lockFile) {
		this.lockFile = lockFile;
	}

	public synchronized boolean lock() throws IOException {
		raFile = new RandomAccessFile(lockFile, "rw"); //$NON-NLS-1$
		try {
			// Fix for bug http://bugs.sun.com/view_bug.do?bug_id=6628575 and
			// https://bugs.eclipse.org/bugs/show_bug.cgi?id=44735
			fileLock = raFile.getChannel().tryLock(0, 1, false);
		} catch (IOException ioe) {
			// print exception if debugging
			if (BasicLocation.DEBUG)
				System.out.println(NLS.bind(Messages.location_cannotLock, lockFile));
			// produce a more specific message for clients
			String specificMessage = NLS.bind(Messages.location_cannotLockNIO, new Object[] {lockFile, ioe.getMessage(), "\"-D" + BasicLocation.PROP_OSGI_LOCKING + "=none\""}); //$NON-NLS-1$ //$NON-NLS-2$
			throw new IOException(specificMessage);
		}
		if (fileLock != null)
			return true;
		raFile.close();
		raFile = null;
		return false;
	}

	public synchronized void release() {
		if (fileLock != null) {
			try {
				fileLock.release();
			} catch (IOException e) {
				//don't complain, we're making a best effort to clean up
			}
			fileLock = null;
		}
		if (raFile != null) {
			try {
				raFile.close();
			} catch (IOException e) {
				//don't complain, we're making a best effort to clean up
			}
			raFile = null;
		}
	}
}